The present invention relates to a universal joint for a drive shaft or a Cardan shaft and in particular to a joint yoke or fork wherein the individual yoke arms or fork arms can be separated from each other and are secured to each other.
A universal joint usually joins a drive and a driven shaft and includes as its major components a first yoke or fork attached to the end of of the shafts, a second yoke or fork attached to the end of the other of the shafts and a spider or cross having pairs of opposite, outwardly directed pins disposed between the forks and between the arms of the forks, which are otherwise known as the bosses of the yoke. Each fork arm or boss receives one of the pairs of pins, so that the yoke will pivot around an axis defined by the respective pairs of pins for that yoke.
Such a universal joint is known from Federal Republic of Germany Allowed Application No. DE-AS 25 55 667, The torque which can be transmitted by the shaft connected to one half of the joint is determined by the strength of the universal joint, and particularly of the spider or cross and of the spider bearing. The internal construction of the bearing determines its life, while the shape of the spider and of the yokes or forks participates in determining the stiffness of the shaft. Measures for increasing the transmittable torque relate to the spider, the bearing and the yokes. With a predetermined structural space or predetermined size of joint, narrow limits, however, are placed on an increase in the size of all of the said components, particularly with due consideration of the angles of deflection which are required in operation. Greater operating strength and longer life are being increasingly demanded on the part of universal-joint shafts with the use of the same or smaller outside dimensions.
It is known that an antifriction bearing of the roller-bearing type has a higer dynamic, but lower static, carrying capacity than a needle-type antifriction bearing of the same size. It is therefore proposed in Federal Republic of Germany Published Application No. DE-OS 26 36 752 (corresponding to U.S. Pat. No. 4,167,859) that the bearing for the spider be equipped with needle bearings in order to be able to install a larger and stronger spider. In the prior art, the purpose was to dimension the spider bearing with the same static load-carrying capacity as the other statically stressed parts of the universal shaft, i.e. spider, yokes, slide piece, etc. This produces relatively small universal joints. However, they do not satisfy the expectations as to life in the case of dynamically high stresses, for instance when they are used as heavy drive shafts in the extreme and intermittent operation of a rolling mill. It has already been recognized that the increase in the size of a roller bearing which is capable of high dynamic loads leads to difficulties in mounting in the case of single-piece yokes and bearing bosses.
In Federal Republic of Germany Allowed Application No. DE-AS 26 25 960, therefore, specially stepped-down rows of rollers have been proposed. The embodiment disclosed in Federal Republic of Germany Allowed Application No. DE-AS 26 53 908 is provided with split bearing bosses or fork arms which make it possible to provide an amply dimensioned roller bearing and a strong spider. However, there is the disadvantage here of the loss of design strength of the yoke or bearing boss or fork arm due to the transverse division of the bearing bosses. A bearing boss of rigid form is, however, necessary with respect to the life of the bearing in order to protect the roller bearing from elastic deformation under load.
U.S. Pat. No. 4,334,415 describes a universal joint design in which the bearing for the spider is developed in one part but is bolted at the end in the manner of a bearing pedestal to the hub, which is developed in the form of a flange. The bolting forms the detrimental weak point of the universal joint. The yoke does not have the required stiffness.